wapm/README.md: document how to test

wapm/README.md

@@ -4,9 +4,37 @@
 
 2. tag
 
-3. build and publish
+3. build
 
 ```shell
 % ./build.sh
+```
+
+4. test
+
+```shell
+% toywasm --wasi ./build/toywasm ......
+```
+
+5. publish
+
+```shell
 % wapm publish
 ```
+
+## Running the binary from wapm
+
+```
+% wapm install yamt/toywasm
+% wapm run toywasm
+```
+
+Or, on toywasm:
+```
+% WAPM_RUNTIME="toywasm --wasi" wapm run toywasm
+```
+
+Note: the stand-alone wapm has been discontinued.
+I don't know what's an alternative these days.
+
+Or, on [webassembly.sh](https://webassembly.sh/?run-command=toywasm).